The Accuracy of Smart Devices for Measuring Physical Activity in Daily Life: Validation Study (Preprint)

Abstract

Background: Wearables for monitoring physical activity are increasingly popular. These devices are not only used by consumers to monitor their own levels of PA, but also by reseachers to track the behavior of large samples. Consequently, it is important to explore how accurately physical activity can be tracked via these devices. The aim of this study was therefore to investigate concurrent validity of three Android Wear smartwatches (Polar M600, Huawei Watch, Asus Zenwatch3) and the Fitbit Charge with an ActiGraph accelerometer for measuring steps and MVPA (moderate-to-vigorous physical activity) on both a day and 15 min level. Methods:A free-living protocol was used in which 36 adults engaged in usual daily activities over 2 days while wearing two different wearables on the same wrist of the preferred hand and an ActiGraph GT3X+ accelerometer on the hip. Validity was evaluated on both levels by comparing each wearable with the ActiGraph GT3X+ accelerometer, using correlations and Conclusions:In sum, all four consumer-level devices can be considered accurate step counters in free-living conditions. This study, however, provides evidence of systematic bias for all devices in measurement of MVPA. The results on a 15-minute level also indicate that these devices are not sufficiently accurate to provide correct real-time feedback.